1. Technical Field
The present disclosure relates to a method of manufacturing an image sensor, and more particularly, to a method of manufacturing an image sensor capable of using alignment keys formed in a scribe lane area.
2. Description of the Related Art
Image sensors are semiconductor devices for converting incident light into electric signals. The image sensors may be divided into two main types of, for example,charge coupled devices (CCDs) and complementary metal oxide semiconductors (CMOS) image sensors.
A charge coupled device may have metal oxide semiconductors (MOS) capacitors adjacent to one another, and the MOS capacitor stores charge and transfers the charge. Meanwhile, the CMOS image sensor may have a plurality of unit pixels for converting charge into a voltage, and outputs signals from signal lines by a switching operation. Due to an increase in the degree of integration of semiconductor devices, the size of a pixel of a CMOS image sensor should therefore be reduced and the degree of integration of the CMOS image sensor should also be improved.
A CMOS image sensor may include an active pixel sensor area in which a plurality of unit pixels are arranged in a matrix and a peripheral circuit area in which peripheral circuits for controlling the unit pixels or processing signals of the unit pixels are formed. For example, the active pixel sensor area may be divided into a photoelectric converter for converting light energy into electric signals and a logic element for processing the converted electric signals to generate data.
With a conventional CMOS image sensor light may be emitted from a lens formed on a plurality of wiring layers to a photoelectric converter through the wiring layers. However, with a conventional CMOS image sensor, an insufficient amount of light may reach the photoelectric converter due to the layout of the multi-layer wiring line. For example, the layout of the multi-layer wiring line may reduce the aperture ratio of the photoelectric converter, which thereby may cause light incident on the photoelectric converter to be markedly reduced, resulting in low sensitivity.
To solve the above-mentioned difficulty, a back-illuminated image sensor has been proposed. With a back-illuminated image sensor, light may be illuminated from the back side (e.g., the side opposite to a wiring portion) of the semiconductor substrate, and the photoelectric converter receives the light. In this way, it is possible to improve the effective aperture ratio without hindrance due to the layout of a plurality of wiring layers and to significantly raise sensitivity as well.
However, with a back-illuminated image sensor, alignment keys, which are used as alignment marks for forming the microlens, may also be needed. Therefore, as a result, an additional process of forming the alignment keys may also be needed.